1. Field of the Invention
The present invention relates to a lightning surge detector adapted to detect a lightning surge current flowing from wire lines of a power line or communications line to a ground wire and display resulting lightning surge information, a surge protective device connected with the lightning surge detector and adapted to protect power supply equipment and other protected equipment from the lightning surge current, and a management system for the surge protective device, the management system being adapted to manage the surge protective device equipped with the lightning surge detector.
2. Description of the Related Art
As described, for example, in Japanese Patent Laid-Open No. 2005-150657 and Japanese Patent Laid-Open No. 2006-059888, surge protective devices according to related art include a lightning protection circuit and a display unit adapted to display a state of deterioration of the lightning protection circuit. When a lightning surge current enters the surge protective device from wire lines of a power line or the like, the lightning surge current is discharged to a ground-wire side by the lightning protection circuit, protecting power supply equipment and other protected equipment connected to the wire lines.
The lightning protection circuit is made up of a lightning protection device such as an arrester or varistor, where the arrester is a lightning protection tube and the varistor is a non-linear resistive element. The lightning protection device will undergo degradation of characteristics when the number of operations increase as a result of lightning surge currents. This may result in burnout due to heat generation. Thus, the display unit adapted to display the state of deterioration of the lightning protection device is provided in the surge protective device.
The display unit of the surge protective device described in Japanese Patent Laid-Open No. 2005-150657 is made up of Thermolabel. The Thermolabel is affixed to the lightning protection device. The Thermolabel changes color with heat generation resulting from operation of the lightning protection device such that changes in the color can be viewed visually.
The display unit of the surge protective device described in Japanese Patent Laid-Open No. 2006-059888 is made up of a coloring member. Furthermore, a disconnect portion is provided to disconnect the lightning protection device from the lightning protection circuit when the lightning protection device deteriorate. When the disconnect portion comes into action, a slide mechanism or swing mechanism causes the coloring member to rotate and thereby change color. Thus, the change in color is configured to be visually viewable through a display window.
However, the conventional surge protective devices described in Japanese Patent Laid-Open No. 2005-150657 and Japanese Patent Laid-Open No. 2006-059888 have problems as described in (1) to (3) below.
(1) Problems with the Surge Protective Device Described in Japanese Patent Laid-Open No. 2005-150657
The Thermolabel of the display unit does not react to low surge currents due to its degree of heat generation. After reaction, the Thermolabel needs replacement because the color of the Thermolabel is irreversible. It is not possible to grasp the number of times lightning surge currents enter. Furthermore, it is not possible to monitor the operations and states of deterioration of plural surge protective devices all together.
(2) Problems with the Surge Protective Device Described in Japanese Patent Laid-Open No. 2006-059888
The display unit is made up of a large number of parts, complicating its structure. Since the large number of display components are housed in the surge protective device, it is difficult to downsize the surge protective device. An attempt to downsize the surge protective device reduces a display area of the display unit, making it difficult to see the display area visually from outside. Furthermore, it is not possible to monitor the operations and states of deterioration of plural surge protective devices all together.
(3) Since the display unit which displays the state of deterioration of the lightning protection device is contained in the surge protective device, even if the display unit is not faulty, if the lightning protection circuit in the surge protective device deteriorates, the surge protective device needs to be discarded and replaced with a new one, resulting in waste. Also, it is not possible to add a discrete display unit to an existing or already-installed surge protective device not preinstalled with a display unit. This is disadvantageous and inconvenient.